Lithium primary and secondary batteries are an important component in developing many energy-related applications ranging from vehicles to consumer electronics. The material properties of lithium, however, present problems in many applications, as well as in the manufacturing process. In particular, lithium foils can be difficult to work with and are not suitable for many important commercial applications particularly when ultra thin layers of lithium are desirable. A general need exists to improve the processability of lithium materials for use in batteries for a wide variety of applications. More particularly, better lithium materials are needed for use in polymer electrolyte batteries and thin film structures. Some efforts have been made to develop lithium deposition methods based on sprays or vapor deposition, but these methods can involve toxic solvents or expensive equipment. Also important is the ability to control the interface between the electrolyte and the lithium electrode, particularly when the electrolyte is a solid and to control dendrite growth for secondary batteries.
Recently, attempts have been made to produce lithium battery anodes from compositions made from lithium powders. For example, PCT application publication no. WO 02/21632 to Xeno Energy Co. describes a lithium powder anode. The anode is made from an emulsified lithium powder in an inorganic oil. However, this reference does not describe use of lithium powder in an ink form. Specifically, this publication does not describe use of lithium powder in combination with a polymeric binders in a solvent. Furthermore, the compositions in this publication are limited to those including lithium powders having relatively large average particle diameters.
U.S. Pat. No. 5,776,369 also describes preparation of lithium powders using an emulsion in hydrocarbon oil. The emulsified particles are filtered from the oil. Particle size is 10 to 100 microns. Korean Patent Application 1994-1781 also describes lithium powders. U.S. Patent Publication No. 2002/0119373 (U.S. Pat. No. 6,706,447) and 2004/0002005 to Gao et al. describe lithium slurries for use in lithium battery anodes. In the disclosed compositions, lithium metal powder and a host material are mixed with a non-aqueous liquid such as THF and a binder, and formed into a slurry. Alternatively, a lithium metal powder can be provided in the anode by, for example, immersing the host material in a suspension containing lithium metal powder in a non-aqueous liquid such as hydrocarbon solvent such as hexane. However, the compositions described in these publications are not formulated to be applied by printing. Instead, the compositions are applied by casting. Anodes produced using the compositions are quite thick, with average layer thicknesses of 50 to 150 microns.
In J. Power Sources, 93, 2001, 145-150), Kwon et al. also describe lithium powder based anodes. The anodes are made from a powder slurry containing lithium powder (20-40 microns), PVdF binder, and THF. Like the compositions of Gao et al, the compositions of Kwon are designed to be cast into anodes and not printed.